Mobile, Alabama's Bay Bridge Road was U.S. 31-90, then some maps showed it as U.S. 31/Alt U.S. 90, then when U.S. 31 was truncated to Spanish Fort, it was U.S. 90 Truck/98 Truck, then around 1999 U.S. 90 was relocated from the Bankhead to replace U.S. 90 Truck, leaving U.S. 90/U.S. 98 Truck. Through in Interstate 10 Detour, which is well signed along the routte, and you have yet another change!

OK-22 was routed through the town of Milburn originally. In 1934, the highway was rerouted over a Farm-To-Market road which bypassed Milburn. In 1935, OK-22 was rerouted through Milburn, and the old alignment became OK-22S. Then in 1936, SH-22 was returned to the bypass. The route somehow ended up back in Milburn by 1939, and the bypass became OK-299, and the two highways swapped places (putting SH-22 back on the bypass yet again) in 1946, the final swap. So between 1934 and 1946, OK-22 was rerouted six times, just counting the changes to that one little stretch. I have no clue why that even happened, either.

US 50 in California has really been changed around. It used to go all the way to the Bay Bridge, then it was cut and changed around a few times, and now it doesn't start until Sacramento. It's been replaced with a bunch of other highways, such as I-580 in the altamont pass and various other routes.

CA-17 is currently the main highway between Santa Cruz and San Jose. Before that...

1940: "New" 17 was opened, replacing the Glenwood Highway and the railroad that connected from Santa Cruz to San Francisco and Oakland

Prior to CA-17 (freeway): 17 went through various main arteries from Milpitas to Oakland (including now International Blvd), then it joined US-40 from Downtown Oakland towards Albany, where it split to the west towards the San Rafael Bridge (formerly via ferry), ending in San Rafael

Until the mid 1980s: CA-17 (freeway) went from Santa Cruz via Milpitas, Hayward, and Oakland towards Richmond and (via the Richmond-San Rafael Bridge) to San Rafael

Nowadays:

CA-17: Santa Cruz to San JoseI-880: San Jose to Downtown OaklandI-580: Stockton via Downtown Oakland to San Rafael

US 50 in California has really been changed around. It used to go all the way to the Bay Bridge, then it was cut and changed around a few times, and now it doesn't start until Sacramento. It's been replaced with a bunch of other highways, such as I-580 in the altamont pass and various other routes.

50 used to run on the following route between the Macarthur Maze (at which point it ran with US 40 and I-80 to US 101) and Sacramento:

I-580 (previously, MacArthur Boulevard) to AltamontI-205 to TracyI-5 to StocktonCA 4 through Stockton (what is approximately the current freeway segment there)CA 99 to Sacramento

Interestingly, the stretch of highway that now carries US 50 between I-80 in West Sacramento and CA 99 has been renumbered plenty of times (though it had US 50's legislative route number in the planning stages!) -

I-80 to Jefferson Blvd & former CA 275 - US 40 in the 1950s, US 40/I-80 in the 1960s, I-80 to 1982, US 50/Business 80/unsigned I-305 from 1982 onCA 275 to I-5 - I-80 from 1966-1982, US 50/Business 80/unsigned I-305 from 1982 onI-5 to CA 99 (approximately replacing former US 99 and CA 24 on Broadway), the WX Freeway - I-80/CA-99 from 1966 to 1982, US 50/Business 80/CA-99 from 1982 to present

Former Route 160 in midtown Sacramento (the 15th/16th Street one-way pair) used to be US 99 between Broadway and N Street, then US 99W in that segment, then finally 160. North of there, it was once US 40/99E, then just US 40, then 160.

The interstate-standard segment of the Capital City Freeway between E Street and US 50 was originally I-80/US 99E, then I-80, and now Business 80/hidden Route 51.

Capitol Mall in downtown Sacramento was originally US 40/99W, then US 40/99W/CA 16, and later CA 275 (now decomissioned).

The current alignment of Interstate 275 between Tampa and St. Petersburg was originally signed as Interstate 4 back when it was constructed in the 1960's. When it was decided to extend Interstate 75 south of Tampa to the Miami area Interstate 4 was truncated to its current terminus at Malfunction Junction in Tampa and Interstate 75 was routed into St. Petersburg, following the former Interstate 4 route. This designation was kept even when the Tampa bypass was first proposed as Interstate 75E. But when AASHTO decided that they did not want any new suffixed interstates, it was decided to run Interstate 75 on the new bypass instead of designating it Interstate 275 as this bypass would redirect the most amount of traffic away from the metropolitan areas. Thus, that section of interstate between Tampa and St. Petersburg was changed once more to its current designation of Interstate 275. This also helps in the clarification of why downtown St. Petersburg has I-175 and I-375, since those two spurs originally were fed off of I-75.

I see a lot of 3-number routes, which happens a lot. Here's a 4: Original NJ 8 was renumbered 8N in the 1920's when NJ first renumbered all its routes, sort of a "placeholder". Then that was renumbered to 84 to match NY 84. Then it was renumbered to 284 when I-84 came through in New York, but there are still signs for "Old Route 84" on one of the old alignments. How about the Holland Tunnel: Originally US 1/9, then just US 1, then Business 1/9, then Business 1, now NJ 139. Somewhere along the way I-78 joined it as well.

17 used to go along the current 880 up to the current 580-80 combine, and then went through Richmond over to San Rafael. The Richmond to San Rafael stretch of the freeway was also numbered as I-180 for a very short time, before it got the current designation of I-580.

I'm not sure the I-180 designation ever existed outside of planning documents (and a few Rand McNally maps) along the freeway from Richmond to San Rafael.

The stretch of what is now I-280 between San Jose Avenue and the Bayshore Freeway has seen several numbers over time: originally, as a segment of US 101A (when 101 was first routed along the Bayshore Highway in the 1930s), then US 101 mainline (when Bypass 101 was applied to the Bayshore by the 1940s), then Route 82 in 1964 when 101 was moved back onto the Bayshore route, followed by I-280 in 1968 when the original 280 routing north along the Junipero Serra Freeway extension to Golden Gate Park was canceled.

The I-215 routing in San Bernardino was originally the surface street routings of US 66 and 91, which then added US 395 at some point. Then as the route was upgraded to freeway, this became I-15 in the initial Interstate plans (with I-15 ending at I-10 and US 395 continuing to San Diego via Riverside). In 1969, I-15 was extended southward down 395, only for it to be shifted westward along the Route 31 and Route 71 alignments a few short years later and the old US 395 routing becoming I-15E/unsigned Route 194.

I-15E survived the 1980 elimination of suffixed non-loop interstates (along with the two I-35 pairs), but was renumbered to I-215 in 1982.

Essentially, US 6 was extended down old Route 7 (now Route 14 and US 395) to the San Fernando Valley, then down US 99 (current I-5) to Los Angeles, and then to a concurrency with Route 11 (present I-110) into San Pedro. This was the point where westbound US 6 joined southbound US 101A heading due east to a terminus at then-Route 15, Atlantic Avenue.

Meanwhille, Route 18 came in from Riverside westward to Lakewood, at which it followed Route 19 south to the traffic circle, and then northbound US 101A (due west) to Atlantic Avenue as well. In the late 1940s, US 91 was added along the Route 18 pathway, thus putting its southern terminus at Route 15 as well (shared with Route 18's western terminus).

When the Long Beach Freeway was built, Route 15 was transferred to that highway (and this became the new terminus for 6 and 91); Route 18 was probably cut back around that point to the San Bernardino area.

In the 1964 renumbering, truncations resulted in this entire segment becoming solely an extension of Route 1. Route 15 became Route 7 (due to the presence of I-15 in the state), which eventually became I-710.

I'm not sure the I-180 designation ever existed outside of planning documents (and a few Rand McNally maps) along the freeway from Richmond to San Rafael.

The stretch of what is now I-280 between San Jose Avenue and the Bayshore Freeway has seen several numbers over time: originally, as a segment of US 101A (when 101 was first routed along the Bayshore Highway in the 1930s), then US 101 mainline (when Bypass 101 was applied to the Bayshore by the 1940s), then Route 82 in 1964 when 101 was moved back onto the Bayshore route, followed by I-280 in 1968 when the original 280 routing north along the Junipero Serra Freeway extension to Golden Gate Park was canceled.

The I-215 routing in San Bernardino was originally the surface street routings of US 66 and 91, which then added US 395 at some point. Then as the route was upgraded to freeway, this became I-15 in the initial Interstate plans (with I-15 ending at I-10 and US 395 continuing to San Diego via Riverside). In 1969, I-15 was extended southward down 395, only for it to be shifted westward along the Route 31 and Route 71 alignments a few short years later and the old US 395 routing becoming I-15E/unsigned Route 194.

I-15E survived the 1980 elimination of suffixed non-loop interstates (along with the two I-35 pairs), but was renumbered to I-215 in 1982.

I -215 was going to be me pick too. I also remembered reading somewhere that before the 1963 renumbering that SR 18 was also part of the same route in san bernardino and riversidelarry